Should I let my doors be drafty if my house is “too tight”?

Question

I had an energy auditor come by and do the door blower test on my house. According to them, my house is considered pretty tight (unfortunately I do not have the number). They were at first going to replace my door seals which are clearly drafty as one of the rooms attached to the garage is always cold, but after the test opted to not do it saying it could make the house too tight. Does it make sense to let my house be noticeably colder because of a drafty door in the interest of prevent my house from being “too tight”? Would changing the seal actually make that much of a difference from a tightness standpoint? Are there any alternatives so I don’t feel like I’m letting heat right out the door?

Answer 1

The main alternative, as installed in most newer "tight" houses, is one of:

• A Heat Recovery Ventilator (HRV)
• An Energy Recovery Ventilator (ERV)

HRVs do heat exchange, only, between fresh air coming in and stale air going out.

ERVs do heat and humidity exchange between the two airstreams. There are a few heating climates where this is helpful, but it's more usually the case that they are better in primary-cooling climates with significant humidity to dehumidify the incoming outside air.

In cold climates you need one with a good defrost scheme for when the outside air is well below freezing.

They are made with various levels of efficiency of heat transfer, (I recall seeing 70-95% when shopping) and generally the better they are at heat transfer, the more they cost, so there's typically a point of diminishing returns when making the buying decision.

Answer 2

I agree with Ecnerwal about solutions, but I thought I'd rant a bit about the whole notion of "too tight" and the misunderstandings the phrase connotes.

A house can only be "too tight" if one or more of these are true:

• Moisture is accumulating in inappropriate places, such as on windows, in the insulation, etc.

• A low-pressure (partial vacuum) condition is created when exhaust fans and HVAC equipment are running

• Indoor air quality is consistently poor

The solution to none of those is to introduce leaks. If that's the takeaway from any energy auditor or other "expert", either the expert is mistaken or the homeowner is. There are almost always more appropriate ways to deal with the problems above that don't include arbitrary, uncontrolled and wasteful leakage, and they should be addressed individually and in suitable ways for a particular case.

Answer 3

"Too tight" is kind of nonsense. A house can't be too tight, you want all air exchange to happen through heat recovery ventilators (basically heat exchangers).

However, as we build modern houses, we drag along obsolete appliances that were designed for drafty houses and whose entire functionality depends on the house being drafty. Let's run through the list of those.

Old school dryers which eject hot humid air to outside. They waste valuable energy 3 ways: hot air that they heated, the 1000 BTU per pound of water evaporated, and house air that you previously paid to condition. It must also keep the ejected airstream hot enough so condensation does not happen inside the dryer vent. The solution is a ventless heat pump dryer that eliminates the vent, recoups the 1000 BTU per pound lost to water evaporation (by re-condensing it and getting the heat energy back for reuse), and not wasting indoor air. So they take typically 500 watts instead of 5700 watts. It's just not wasting energy.

Older 70-80% gas appliances simply steal conditioned house air for combustion, and sends that + combustion products up the flue, using gravity (hot air rises since it is less dense). Since it must keep the air in the flue quite hot to make it move by gravity, that energy is thrown away and that's where the 20-30% goes.

When people talk about houses being "too tight", this is the crux of it - they're afraid if you have a dumb 80% furnace or water heater that relies on stealing house air and gravity flue… and then you run yesterday's dryer or exhaust fan, you'll pull a negative pressure on the house and cause exhaust to run backwards down the flue, filling your house with exhaust.

The modern approach is to separate out the combustion compartment and use 2 pipes so it draws combustion air from outside, and is not stealing it. Even better, this is done with concentric pipes - the exhaust pipe is inside the intake pipe! This acts as a heat exchanger, moving almost all the heat out of the exhaust into the intake. Of course, cold air doesn't rise, so a small electric fan needs to push combustion air out. But that's how you get to 95%.

For water heaters, consider heat pump - they don't make heat with electricity or fuel, they steal it from the utility room, obliging you to run heat a bit more, or A/C a bit less! A pure/genuine (not hybrid) heat pump water heater only needs about 1000 watts. I expect to soon see heat pump water heaters with an outside unit so it doesn't steal heat from the house. Monobloc types will not need freon plumbing.

Then you have bathroom exhaust fan - use a heat recovery ventilator here of the simple kind (not humidity-recovering), so you recoup the heat but not the humidity, as desired.

Kitchen exhaust, same - but you need good filtration to keep the HRV from getting contaminated.

Answer 4

The house should be sealed, BUT have controllable fresh air entry.

This helps keep the heat requirements under control.

If you have a boiler or woodstove needing fresh air for combustion, it should have its own dedicated air supply or a sufficient air entry into the room or space that it is in.

Answer 5

I think the responses are good for someone building a new house or doing a substantial remodel, but Cody is just asking if he should skip putting weatherstripping in the door, or if there is a better solution. In this case, I would put the weatherstripping in the door (as recommended in earlier posts) but then consider one of the whole-house ventilation systems.

There are two levels of ventilation system, some that just push air into the house at intervals you can set. These are ok, but as noted earlier, the heat that you paid for to condition your house will be replaced with cold (or hot) unconditioned air from outside. Depending on the climate where you live, this may or may not be big deal, but in areas where the temperature varies greatly it might be a problem.

Another option is to install a whole-house ventilation system that has an integrated heat pump. One example is the Pioneer ECOasis 150 (not an endorsement, just an example), which will provide heating or cooling with incoming air. These cost a little more, but would provide fresh air that is conditioned and filtered. Obviously, if you could capture the existing conditioned air and use that to pre-condition the outside air it would be better, but that involves a lot of complex design and piping, which for some houses might not be practical and cost prohibitive.